The present invention is directed to a fire door and a method for its manufacture. More particularly, a fire door made of resin and vermiculite that is suitable for use as a decorative entry door is disclosed.
The use of fire doors in buildings is an important factor in avoiding injuries and loss of lives and in preventing property damage as a result of the door""s ability to impede the spread of fire. In the interest of public safety, standards have been set by governmental agencies, building code authorities, and insurance companies for the installation and performance of door assemblies which retard the passage or spread of fire. Building codes require that fire-resistant door assemblies pass standard industry-wide tests that are an evaluation of the fire-resistant properties of the door assembly in relation to heat and flame for a specified duration.
Fire doors have always presented one or more of several different problems to architects, designers, and builders. Fire doors are sometimes very expensive and complicated to manufacture, or require expensive materials for their construction. Still other fire doors transmit heat readily, or are so heavy that they require special construction in the door frame before they can be hung, or require special hardware. Because of the costs incurred overcoming one or more these problems, many fire doors are too expensive to manufacture and are not used as often as might be desirable.
A fire door must have certain basic properties in order to meet standard industry-wide fire endurance tests, such as those in accordance with UL 10C (1998), NFPA 252 (1995), and UBC 7-2 (1997). In these tests, the door and frame are exposed to intense heat, such as that generated by fire in a burning building. Exemplary conditions of such tests involve exposing the door assembly to temperatures which progressively increase within the range of 1750xc2x0 F. to 1800xc2x0 F. for an exposure period up to 1xc2xd hours. A door meeting these standards is rated as a 90 minute door. The disclosed door may actually withstand longer term exposure to fire conditions. Basic properties that must be possessed by door cores during exposure to such tests are discussed below.
The fire door typically has a core, which itself must have good integrity during exposure to fire, that is, it must resist heat transfer, burning, melting, spalling, cracking, bowing or deteriorating in any way which would cause the temperature, on the side of the door not exposed to the fire, to rise to the extent that the combustible veneer on the unexposed side of the door burns or chars substantially.
During exposure to heat, the core must also exhibit good dimensional stability. It must remain relatively stable and resist warping or shrinking to the extent that it remains in contact with the banding (stiles and rails) around its perimeter. Separation from the banding can cause the combustible components to bum away prematurely, allowing fire to penetrate the opening.
In addition to the foregoing properties, the core must be resistant to heat transmission such that the transfer of heat from the fire-exposed side of the door to the unexposed side is deterred. Otherwise, ignition and possible spread of fire may result from premature charring or burning of the combustible veneer of the unexposed side on the door.
Another characteristic required of the core is that it must retain its integrity when exposed to a hose stream. After the door is removed from a heat source used for conducting the fire endurance test, it is subjected to the sudden cooling effects of a hose stream. The core must retain its integrity under the pressure of the hose stream.
In addition to possessing the foregoing properties, fire doors must, in order to be commercially acceptable, have other properties that arc related to the manufacture, installation and service of the fire resistant door. For example, the door must have sufficient strength, yet be light enough in weight to allow it to be hung and used without becoming unattached from its mounting. One measure of this property is the screw-pull strength, i.e., the force required to pull out a screw installed into the door. Another test is the ability to withstand repeated cycling, i.e., the door""s ability to satisfactorily withstand repeated opening and closing.
Those skilled in the art will recognize that there is a need for a fire door which is effective to retard the penetration and spread of fire or the transmission of heat. Yet a further need in the art is a relatively strong and durable fire door that is sufficiently light to avoid the trouble and expense of special door frame structures on which to hang the fire door, and is relatively easy and inexpensive to manufacture.
It is therefore a primary object of the invention to provide a fire door meeting these needs in the art. More particularly, it is an object to provide a fire door well suited for entry doors.
The inventor has discovered that these needs may be met by a fire door which comprises a generally rectangular core formed of resin bonded exfoliated vermiculite having a predetermined density. A pair of stiles are secured to and extend along opposed edges of the core, and a pair of rails are secured to and extend along opposed edges of the core. The stiles and rails are formed of resin bonded exfoliated vermiculite having a density exceeding the density of the core.
A fire door, according to another aspect of the invention, comprises at least a first rectangular core formed of resin bonded exfoliated vermiculite. The core has first and second major surfaces and four peripheral edges. A recess is formed in and extends along each of the edges. A pair of stiles and a pair of rails are provided, wherein each of the stiles and the rails are formed from resin bonded exfoliated vermiculite. Each of the stiles and rails has a tenon extending therefrom, and each of the tenons is adhesively secured within an associated one of the recesses.
A method of assembling a fire door, according to yet another aspect of the invention, comprises the following steps. A generally rectangular door core formed from resin bonded exfoliated vermiculite is provided. A pair of rails and a pair of stiles formed from resin bonded exfoliated vermiculate are also provided. The stiles and rails are adhesively secured to the peripheral edges of the core.